Minor cleanup in inferrer folder

pkg/compiler/lib/src/inferrer/list_tracer.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-part of type_graph_inferrer;
+library compiler.src.inferrer.list_tracer;
+
+import '../elements/elements.dart';
+import '../universe/selector.dart' show Selector;
+import '../util/util.dart' show Setlet;
+
+import 'node_tracer.dart';
+import 'type_graph_nodes.dart';
 
 /**
  * A set of selector names that [List] implements, that we know do not
  * change the element type of the list, or let the list escape to code
  * that might change the element type.
  */
 Set<String> okListSelectorsSet = new Set<String>.from(
   const <String>[
     // From Object.
     '==',
@@ skipping 184 matching lines @@
         callsGrowableMethod = true;
         assignments.add(inferrer.types.nullType);
       }
     } else if (selector.isCall &&
                !info.targets.every((element) => element.isFunction)) {
       bailout('Passed to a closure');
       return;
     }
   }
 }